The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Generally, a cooler is an apparatus which cools an engine to prevent the engine from overheating and maintain the engine at an operating temperature. The cooler have used an air cooling type which uses external air to directly cool the outside of the engine and a water cooling type which circulates cooling water into the engine to cool the engine.
As illustrated in FIG. 1, the water cooling type cooler is configured to include a water jacket 30 configured enclosing a cylinder 10 and a combustion chamber 20, a water pump 40 pumping water into the cylinder 10, a radiator 50 transferring heat of high-temperature cooling water to external air to cool the cooling water, a fan 60 assisting with ventilation of the radiator 50, a thermostat 100 for rapidly increasing a temperature of the cooling water to an operating temperature just after starting, etc. By this configuration, the water pump 40 circulates the cooling water into the water jacket 30 enclosing the cylinder 10 to cool heat generated from a cylinder block 70 and a cylinder head 80 and then the radiator 50 draws the cooling water warmed in the water jacket 30 to radiate the heat of the cooling water. Further, the water of which the heat is radiated from the radiator 50 is again circulated into the water jacket 30 to cool the engine.
Further, the fan forces the external air to come into contact with the radiator 50 to improve a heat radiation effect. Further, the thermostat 100 is installed in an upper channel 90 between the water jacket 30 and the radiator 50 and is controlled to be automatically opened and closed depending on a change in the temperature of the cooling water to control a flow rate flowing in the radiator 50 so as to maintain the temperature of the cooling water at an operating temperature, thereby switching a circulation path of the cooling water depending on the temperature.
An operation of the thermostat will be described below in more detail with reference to FIGS. 2A and 2B. FIG. 2A is a cross-sectional view illustrating a state in which the thermostat is closed and FIG. 2B is a cross-sectional view illustrating a state in which the thermostat is opened depending on the increase in the temperature of the cooling water inside the water jacket. As illustrated in FIG. 2A, if the temperature of the cooling water inside the water jacket rises beyond a defined temperature in the state in which the valve 10 is closed, a wax 125 inside a pallet 120 is expanded to compress a rubber 130 inserted into the pallet 120, such that a spindle 140 at a central portion of the rubber 130 may be pressurized upward. However, the spindle 140 is fixedly mounted on the bracket 150 and therefore the pallet 120 falls, such that a valve 110 may be opened as illustrated in FIG. 2B.
As illustrated in FIG. 2B, the valve 110 is opened to circulate the cooling water warmed in the water jacket into the radiator. As a result, if the temperature of the cooling water falls, the expanded wax 125 is contracted and the compression of the rubber 130 is removed, such that the pallet 120 returns to an original position by elasticity of the spring 160 as illustrated in FIG. 2A.
However, when the valve is opened even below the preset temperature due to the fault of the thermostat, the cooling water is continuously cooled by the radiator, and therefore the amount of heat lost by cooling among heat generated by the combustion is increased, thereby reducing heat efficiency of the engine, an ECU controlling a fuel injection amount based on the temperature of the cooling water increases the fuel injection amount to increase power consumption since the temperature of the cooling water is low, and a mixer making atomization of gasoline insufficient in a cylinder is provided to dilute engine oil with the gasoline and promote a cylinder wear. Further, a larger amount of exhaust gas is relatively generated than in a normal condition, which affects performance of other self-diagnosis apparatuses (oxygen sensor diagnosis, catalyst abnormality diagnosis, exhaust gas recirculation apparatus diagnosis, evaporation gas system leakage diagnosis, etc.).
As described above, the thermostat controls the temperature of the cooling water of the engine. In particular, when a flow stop valve is applied to the vehicle, a difference in the rising tendency of the temperature of the cooling water may occur. When the flow stop valve is applied, the rising in the temperature of the cooling water is rapid at an early time and even when the flow stop valve is normal and the thermostat is faulty, due to the flow stop valve, the rising in the temperature of the cooling water does not show a large difference from the case in which the thermostat is normal.